It took 19 men to hijack four airliners and crash them in New York, Washington and Pennsylvania on Sept. 11, 2001, killing nearly 3,000 people.
But a much larger network of conspirators was involved in planning, funding and carrying out the attacks, and governments around the world have been after them ever since.
Some have been captured or killed and some remain at large or unidentified. A decade later, more than half of those charged in the United States have yet to stand trial.
The following people have been convicted, charged, investigated or named as co-conspirators in legal proceedings connected directly to the Sept. 11 plot and attacks